Bituminous sands are among the major hydrocarbon resources. However, these resources involve development difficulties due to their high density and viscosity, and they generally have an API degree below 10° API. They come in form of an organic component and a mineral component. The organic component is also referred to as bitumen. The mineral component is for example made up of sand, clay, metals or metallic oxides. Typically, a bituminous sand has an organic component that represents approximately one tenth of its mass, but this proportion can be highly variable.
In the case of bituminous sands extracted from a mine, most methods for separating the bitumen from the sand are based on the flotation method developed by Clark. It consists in bringing the bituminous sand into the presence of hot water (generally at 82° C., a temperature at which the density differential is maximal between the bitumen and the water) and soda (at a concentration ranging between 0.03 and 0.1 wt. % NaOH), as described in the article “The Chemistry of Alberta Oil Sands, Bitumens and Heavy Oils, O. P. Strausz, E. M. Lown, Alberta Energy Research Institute, Calgary, Alberta, Canada, 2003, p. 57-67”.
The separation mechanism corresponds to a separation by flotation where the bitumen forms a foam by becoming attached to air bubbles, the sand settling in the bottom of the treatment reactor. Three streams are produced: a solid stream containing the sand and less than 5% bitumen, a basic water stream containing a small percentage of the bitumen (around 5 wt. %) and a foam containing nearly all of the initial bitumen (fraction above 90 wt. %). The aqueous phase is treated with an organic solvent (of gasoline type) in order to recover the bitumen and to increase the bitumen recovery rate so as to raise it to above 95%.
In the case of deep bituminous sands, the separation method generally used consists in injecting vapour under pressure into the geological formation containing the bituminous sand. The heat supplied by the vapour fluidifies the organic component that then flows downward to the bottom of the formation through gravity and is recovered through dedicated underground lines.
Whether in the case of an in-situ method wherein vapour is injected into the ground and bitumen is directly recovered, or in the case of a mining method wherein the bitumen is extracted from the ground with the sand, then separated with hot water and soda, large amounts of water and of heat are necessary. In nearly all the cases, the heat is supplied by the combustion of natural gas imported on the production site, without capture of the carbon dioxide (CO2) produced. This involves connection of the site to the natural gas network, often distant from the production sites, and combustion of natural gas whose price evolves with that of oil and is going to rise in the forthcoming years. The order of magnitude of natural gas consumption ranges from 10 to 30 m3 natural gas burned per barrel of Athabasca produced, depending on whether the bitumen is respectively recovered by surface mining or by steam-assisted gravity drainage (Canadian Energy Research, CERI study No. 108 in “Overview of Canadian Oil Industry”, 2004). For a production of 100 000 barrels/day, the total natural gas consumption is above 300·106 m3/year.
Chemical looping combustion is an oxycombustion type method wherein a hydrocarbon is oxidized on contact with an oxygen-carrying solid. Its operation is based on the reversible shift of this solid from one oxidation degree to a second, by gain or loss of oxygen atoms depending on the medium and on the reaction conditions. To achieve this alternation, one option consists in using a circulating bed where the solid is carried from an oxidizing reaction medium to a reducing reaction medium.
This complex technology has been the subject of many patents mainly based on the combustion of feedstocks nearly predominantly made up of hydrocarbons, whether gaseous (U.S. Pat. No. 5,447,024), liquid or solid (FR-2,850,156).
The applicant has developed a process for treating feedstocks such as bituminous sands or oil shales comprising both a mineral component, such as sand or clay, and an organic component, such as a bitumen type hydrocarbon, the energy required to operate the process being preferably provided by the combustion of this organic component under chemical looping combustion conditions. This energy production mode is particularly interesting within the context of bituminous feedstock extraction insofar as it allows to develop a local unrefined energy source while allowing the environmental impact to be limited through easier capture of greenhouse gases, more particularly CO2, and through potential water resources saving.